Sound deadening composition



106. CDMPOSITIONS,

COATING OR PLAST|C.

Patented ar. 12, 1

UNITED STATES PATENT OFFICE SOUND DEADENING COMPOSITION Benjamin Fosterand Carl J. Seydel, Philadelphia, Pa., assignors to Benjamin FosterCompany, Philadelphia, Pa., a corporation of Delaware No Drawing.Application July 30, 1938, Serial No. 222,294

2 Claims.

This invention relates to methods of making. and to the products, sounddeadening compositions that are also fireproof. The invention isparticularly concerned with the methods of making, and the resultingproducts, of bituminous compounds which are used in sound and heatinsulating installations.

The art of sound deadening and insulating metal vehicle bodies, such asautomobile, train, airplane, and railway box cars, and the sounddeadening and insulating of metal ventilating and air-conditioningducts, metal wall partitions, metal doors, etc., has been highlydeveloped in recent years. However, nearly all of the products used haveserious objections which are due to the fire hazard present. This hazardexists because, either the sound deadener, or insulator itself, is notfireproof, or because the cement used to fasten a fireproof deadener inplace on a structure is not fireproof.

This invention has for its objects to provide a sound deadening andfireproofing composition which may be applied to the surfaces of metalstructures of all kinds, either as a,plasiic..cemiig to be applied witha trowel, or sprayedmpnathe surfaee-to-be-oeated; or asuitable fabricsuch as burlap, or sheet asbestos, may be sajgrated with thecomposition, and the saturated sheet then secured to the surface to becoated by a layer of the plastic composition, and thereafter anotherlayer of the plastic composition may be sprayed or otherwise applied tothe installed saturated fabric sheet. Other methods of applying theplastic composition are described herein.

By sound deadening we mean the actual deadening of the tone emitted by apiece of metal, which of course has been set in vibration, and which hasbeen treated by the application of some material applied for thispurpose. This "deadening effect is brought about, conventionally, by theapplication of a bituminous plastic material, or by cementing a piece ofsaturated or unsaturated roofing felt to the inside of the outsidepanel. The above method of deadening is most generally used on metalautomobile bodies. In the case of a metal railroad coach or car a thickpad of hair felt is sometimes used. This is fastened in place with anasphalt adhesive. The eiiect of these materials is to lower the "naturalfrequency of the vibrating panel, and to slightly decrease the totalvolume of sound emitted, and to act as a damper on the panel therebyshortening the duration of the sound. As an illustration, a sheet steelpanel about 20 inches by 20 inches by one-fourth inch thick, willnormally vibrate at a frequency of about 140 cycles per second. Such asteel panel, uncoated, when set in vibration will continue to emit anaudible tone for about 25 seconds, whereas after coating with anefficient "sound deadening composition will become silent in about 8seconds; and in some cases, in a still shorter time. This shortening ofthe duration of the time of the sound is called the decay time.

Again referring to the bituminous plastic materials" which areextensively used, these compounds consist of an :edissglvedimm mineralor coal tar sgl to which is added a pr Em 1g so mng points. The solventsvary from slow to quick drying volatile distillates. The fillers vary inparticle size and composition. There is generally, but not necessarily,asbestos fibre present, either alone, or in com na ion with the otherfillers, which latter may be granulated cork, ground mica, ground charcoahpawdered mineral mattE'E'Torexample talc 9:99?" -dered-sand, orfireman material. Another sound deaTd'i'ierTbut one Which'isnot soextensively used, consists of a clay type sion, either alone origmentegl with the fille'r's E'Esb'fibed above, and somecases weightedwith a suitable grade of sand.

The plastic type o'Tsound deadener described above is generally appliedin thicknesses of inch to inch, by using a spray gun made expressly forthis purpose, or by brushing, or trowelling.

The objections to these types of products are many, but the greatest oneis the fact that none of them are fireproof, The solvent type sounddeadener is easily burned either in the wet or dry state. The asphaltemulsion type of sound deadener is not easily burned in the wet state(it is necessarily not combustible because of the water present) but isrelatively easy to burn in the dry state.

The primary importance of a sound deadening material is efliciency."This of course will embody such requirements as: sound deadening value,flre resistance, ease of application, resistance to wear, adaptabilityto plant conditions such as (in the case of automobile bodies) baking,oil baths, alkali baths, etc. Of secondary importance, but nearly asgreat as emciency is low cost. This not only refers to original cost pergallon, or pound, but also to the finished or applied unit cost. It isobvious that the more efficient a deadener per gallon or poimd, the

e asphalts vary from low to V Examiner smaller the quantity required toproduce a desired efiect.

The invention described herein meets all of the requirements outlinedabove, together with 5 several other desirable characteristics. In thefirst place it is fireproof in both the wet and dry state. Also, whenapplied with the aid of an air gun the pressure required to force thecompound from the pressure tank to the gun is in the neighborhood of 35pounds per square inch, or less, as compared with the conventional 80pounds per square inch minimum required for inflammable sound deadeningcompounds. With the new type there is no danger of explosions in thepressure tank, and practically no deteriorating action on the rubberhose which is used to supply the gun from the pressure tank.

It is common knowledge that bituminous materials such as asphalt, pitgh,rosin, and gsins, etc., are more or less waterproof. They are Eer'tainlyinsoluble in water. They are also thermoplastic. It is possible toprepare dispersions of these products in water, but no solution takesplace. This particulaTart of dispersing bitumens in water is quite wellcovered by the prior art. It is not only impractical but impossible todissolve the common inorganic salts in either asphalt or pitch. It istherefore not possible to take advantage of the fire resistingproperties of these salts by any method known to date.

discovered a method of incorporating certain g1grganiosalts with asphaltor pfl'ch, and we obtain as a result a compound which is an excellentsound deadener, and also pomesses the desired fireproof qualities.

In the manufacture of our sound deadening bituminous compound, severalmaterials can be used, and as many or more ways of combining them. Forexample, we can first prepare a cla type bituminous emulsion consistingof approximately 40%-4 as halt, 5%-'7% cla and 48%-55 w. To thispreparefii'ilsion we can mix in approximately twice its weight of asolution of my water soluble fire roofing agent. This fireproofing agentcan be a 5570 5570 [or greater if so desired) solution of any of thefol- -a lowing: so i state, ammonium-magnesium hos a e, sodium borate,We calcium chloride, or omum silicate. 60 owever; Because of cost, we'pre er to use solution of sodium silicate. This is a commercial productand is commonly known as water lass, silicate of soda, and sodiumsilicate." How- 'ever, 15 1s commercially available as a thick so- 66lution having varying gravities, and is designated as 405060 etc. Banm.In our composition we can use any of these grades depending upon thecharacteristics which we desire to impart to the product. After theaddition of our fireproofstirring in, for example 15%-20% by weight ofF351; fibre and an equal quantity of granuated cork or mica, orcharcoal, or a similar material, o a su a e m1 ereof. If we so 05 desirewe can adjust the consistency of this finished product to enable it tobe sprayed, brushed, or trowelled, simply by the addition of morefillers (if we desire it to be stiiIer), or by the addition of thecombined asphalt emulsion and fireproof- 70 ing solution (if we desireit to be thinner).

"Ihdbhibxample of how we can prepare the fireproof bituminous compoundfollows-we can prepare a clay type bituminous emulsion in theconventionmer'anmefiadd directly to 75 this emulsion the fillersmentioned in the foreclng agent we can add to the mix a filler by simplyWe have fireproof bituminous compound and which we can 10} use if we sodesire, but which should be used soon after preparation, consists ofpreparing an ashaltic cutback in the usual manner. That 155 melting theas halt and while still molten adding a volatile solvent to reduce theconsistency to a 15 ChlCE solution when cold, or at room temperature. Wecan also use any of the asphalt cutbacks which are commerciallyavailable. In either case, whether we prepare the cutback, or purchaseit in its liquid form, we simply mix in the fillers 20 which againconsist of asbestos, mica, ground 25k, charcoal, etc. The proportionsare the same as'given in the last example, namely, 30 7 1- 40% asbestos,and 30%-40% of the other materials. esultant product is a heavy plastic25 material. To this we simply add the aqueous salt solution andthoroughly mix it in. When making t is of compound it is necessary toadd the preferred salt solution (silicate of soda) slowly, in order thatno subsequent sepaimakes place. 30 The quantity of fireprooflng agentwill be approximately twice that of the combined cutback and fillers.

It is possible to make any or all of the described mixes by hand, thatis, by stirring together the 35 various materials; but it is desirablein commercial practice to use a power driven mixer. This mixer can be apaddle type horizontal or vertical device, or it can be the so-calledribbon type" mixer. This latter type differs from the paddle 40 typeonly in that it has a series of ribbon-like arms fastened to the ends ofthe paddles. It is desirable to maintain a peripheral speed of fromabout 100 to 150 feet per minute when loaded.

In order to secure certain characteristics in the 45 fireproofbituminous compound, we can vary the melting point and penetratiqngf theasphalt used; or we can vaTy the grade of silicate'ofs'oda or otheraqueous salt sgl utpmemfexample, if we desire a bituminous compoundhaving a very quick set and which, when dry, will be quite plastic, wecan use a solution of sodium silicate having a Baumg gravity of saymiidan'as phalt cutback or an Wesson prepared ifofn a s aft asphaltwltl'i'f'iiltifig'pfiint of about 90- 95 F. (ball and ring). Ifwe desirethe same setting time, and want the dried film to be quite hard, we canuse a cutback or emulsion made from an asphalt having a melting point ofabout i90-200 F. (ball and ring). If on the other hand we desire a slowsetting bituminous compound, we can use a solution of silicate of sodawith a Baum gravity of about 60. By varying the melting point of theasphalt we can have the dried film either soft nhard, as we may choose.Also it is possible to obtain combinations of these properties by usingan asphalt with a melting point somewhere between 90-200 F. (ball andring), and a solution of silicate of soda having a Baum gravitysomewhere between 40-60.

The sound deadening composition prepared in any suitable manner, is athick viscous mass at ordinary temperatures, and as noted above may beapplied to a vertical surface to a thickness of as much as three-eighthsof an inch without 76 flowing or sagging. During air drying, a settingoccurs, the entire mass self-welds and hardens into an impervious anddurable non-brittle layer. The asphalt or similar bitumen has theproperty of imparting a permanent adhesive or wetting" property to driedinorganic salt fllms, for example, sodium silicate films, when the wetplastic is applied to a metal surface.

The prepared sound deadening compositions ready for application, may beapplied at ordinary temperature, about '70 F. They may be applied tocold or hot (upwards to about 200 F.) metal surfaces. The compositionsmay contain ingredients in the following approximate proportions: in theas halt cutback type, .the asphalt may be presen in from about 15% toabout 20%; in the play; 1 e the emulsion may be present in from about15% to about 30%. With both types, there may be about 15% of volatilesolvent present. The filler, including asbestos, cork, tal c, etc., maybe present in from about 6%120 about 10%. The aqueous soh tgn pfinorganic salt, for example, sodium silicate as descri 'h'efin, may bepresehFififi'dhTabout to about After air drying for a week or longer,the water content in the dried coating will be from about 5% to about7%.

The improved sound deadening bituminous compounds described aboveexhibit properties which are quite foreign to previous bituminousadmixes. For example, if any of them is applied to a piece of steel orother metal, it readily adheres to it even though it be in thickness ofthreeeighths inch or more. When freshly applied the compound can besubjected to the open flame of a Bunsen burner without showing anyevidence of burning; the flame can be applied to either the coated oruncoated side of the metal. If this test is conducted on theconventional cutback type deadener (which contains no aqueous saltsolution), it immediately catches flre and burns if the flame is appliedto the coated side of the metal. If the flame is applied to the underside or uncoated side, as soon as the solvent is slightly heated itflashes and burns.

When the uncoated side, or coated side, of a metal panel to which hasbeen applied our improved sound deadening bituminous compound, is heatedwith a Bunsen burner flame the volatile solvent and the water areevaporated together and prevent the ignition of the said solvent. Thesilicate of soda or other salt then fuses and prevents the furthervaporization of the asphalt. It is not our intent or purpose to heat apanel containing this compound to such a degree that the silicate ofsoda or other salt fuses; but in the event that sufllcient heat beapplied. this fusing Lxammer action will take place and prevent theignition of the dried compound. When this fusing action has taken placethe sound deadener coating no longer has its original sound deadeningproperties. One test, which demonstrates the fire resistance of the wetfilm, was conducted by spraying a one-fourth inch thick coat of thesound deadening bituminous compound upon a 19 gauge cold rolled steelsheet, two feet square. While still wet, this panel was cut in two byusing an oxy-acetylene flame. No burning of the compound was detected.It fused quite hard adjacent the cut but did not flame or burn. When thesame test was conducted on the conventional cutback type sound deadenerit was impossible to cut the sheet in half until all of the solvent andthe asphalt had burned out of the mass. These tests, of course, arerelated here for the sole purpose of demonstrating the fire resistanceof the new compound. However, there are occasions, during themanufacture of a bus, for example, where slight mechanical changes orrepairs must be made shortly after the application of the sound deadenercomposition. When such changes necessitate the use of electric or gaswelding, the possibility of serious fire damage is present when theconventional cutback type deadener is used. This fire hazard, as alreadypointed out, is not preesnt when our improved sound deadening bituminouscompound is used.

When our improved sound deadening bituminous compound is appliedone-fourth inch in thickness upon metal, it can be either oven dried attemperatures up to 350 F. without sagging out of its original position,or without slipping or running or blistering. It also can be air driedand then subjected to temperatures 0 e or er of 350 F. and still retainits original form. After either air dryingmr oven baiting, it willwithstand the same fiamet"esfs'as the wet film. Air drying requires from24 to 48 hours.

We claim:

1. A homogeneous sound deadening composition comprising from about 15%to about 30% of an aqueous clay type emulsion of thermoplasticbituminous material, from about 6% to about 40% of a filler, and notless than about 30% of an aqueous inorganic salt solution ofsubstantially a 50% to about 60% concentration, said inorganic salthaving fireproofing properties.

2. A sound deadening composition, as in claim 1, in which the aqueousinorganic salt solution is a solution of sodium silicate of about 40 toabout 60 B., and is present in from about 50% to about 70%.

BENJAMIN FOSTER. CARL J. SEYDEL.

